You need to first make everything positive:
x^2=36
Then you need to get the square root of each side:
x=6 or -6
Hope this helps :)
Assuming the sheet is a square
see diagram
the length will be 20-2x
the width will be 20-2x
and the height will be x
the volume will be (20-2x)(20-2x)(x)
Answer: I forgot i remember the answer in my head I forgot..
Step-by-step explanation: